Hello asitdutta, and welcome to the forums.
If you will note this post: IMPORTANT NOTICE TO ALL LETTER WRITERS: READ THIS BEFORE YOU POST, you will see that we do not write letters for people.
You must attempt to write the letter first. Pretend you are standing in front of the person you are writing to, and write down what you would say in person.
That said, I'm not sure what you are asking. Who are you apologizing too? When did you start work?